Not Applicable
Not Applicable
The present invention relates to a process of preparing polyester resins. More particularly the invention relates to a method of preparing polyester resins using dicyclopentadiene (DCPD) where the resins have reduced levels of gel particles or which are free of gel particles. DCPD is commonly obtained as a complex mixture of various components derived from a cracking operation. The predominant component of the mixture is the dimer of cyclopentadiene (CPD) dicyclopentadiene. Commercially DCPD is available in a number of grades. Present in most grades are adducts of CPD with isoprene referred to as C-10 co-dimers in addition to other co-dimers and low molecular weight materials. The lower purity grades contain various and increasing amounts of C-15 isomers (trimers) of CPD. The trimer component is important because it is believed that the higher the trimer content the greater the amount of gel particles formed during standard resin processes. Lower grade DCPD can have as much as 2% by weight trimer while typical xe2x80x9cpolyester gradexe2x80x9d DCPD has less than 0.1% trimer content. Trimer content is not the sole cause of gel particle formation. On occasions where lower grade DCPD has been diluted with xe2x80x9cpolyester grade DCPD to contain less than 0.1% by weight trimer, gel particles can still be a problem.
DCPD modified polyester resins are known. See for example U.S. Pat. Nos. 3,347,806, 4,029,848, 4,148,765 and 4,233,432. Typically, resins are prepared using the higher purity or xe2x80x9cpolyester gradexe2x80x9d DCPD. A general method of preparing DCPD modified polyester resins includes the steps of preparing the half ester by reacting a carboxylic acid or anhydride with polyester grade DCPD in the presence of water. The reaction is normally carried out at atmospheric pressure and a temperature high enough to ensure that the DCPD reacts with the acid or anhydride but is not high enough to cause the DCPD to decompose. The reaction is carried out to a predetermined end point for the half ester formation. This point can be conveniently determined by measuring the acid value of the reaction mixture. Once the predetermined end point of the half ester reaction mixture is reached, multivalent alcohols are added and allowed to react to a predetermined end point. This end point can also be determined by monitoring the acid value. Economically it would be desirable to use the less expensive lower grade DCPD, but the use of the lower grade DCPD tends to yield polyester resin that contain gel particles. Gel particles are undesirable in part because they are a contaminant in the resin and tend to plug spraying equipment and filters. In order to remove the gel particles the resin must be filtered. Although resins may be filtered to remove minor amounts of particulates the presence of gel particles causes increased problems due to filter fouling. The gel particles also represent a reduction in the percent yield of resin in a batch. So while it would be desirable to use low grade DCPD in polyester production the costs associated with dealing with gel particle formation offsets the lower material cost. Efforts have been made to prepare gel particle free polyester resins using low grade DCPD. U.S. Pat. No 4,360,634 discloses polyester resins made using diene oligomers. According to the patent the product can be prepared using standard methods of preparation for DCPD modified polyester resins. The stated advantage of the invention is the use of oligomers of crude DCPD prepared by heating the crude diene under a pressure of from 100 to 200 psig at a temperature of from 150xc2x0 C. to 200xc2x0 C. for a period of from 30 minutes to 4 hours prior to adding to the ester reaction. Korean Patent No. 98-026116 discloses a method of preparing DCPD modified polyester resins using low purity DCPD where the formation of gel particles is reduced. The method discloses the reaction of 70% to 80% pure DCPD with multivalent unsaturated acids in the presence of an oxidation preventing reagent and/or a polymerization preventing agent. It is stated that although the half ester method can be used the invention is not limited to any one method. U.S. Pat. No. 5,777,065 discloses a method of making polyester alkyd resins having reduced gel particle content where prior to adding a low purity DCPD, from 10 to 300 ppm of an aromatic inhibitor is added to reaction mixture.
The present invention relates to a process for preparing polyester resins free of or substantially free of gel particles even when low purity DCPD is used. The process comprises forming the half ester and then raising the temperature of the half ester reaction mixture to from 165xc2x0 C. to 220xc2x0 C. and holding the reaction mixture at the desired temperature for up to 120 minutes while optionally removing volatiles.
The formation of the half ester can be carried out using process parameters typically used in the preparation of DCPD modified esters. In practice it is preferable to perform the half ester reaction step at atmospheric pressure and a maximum temperature of 150xc2x0 C. After the half ester step is complete but before addition of the multivalent alcohol the half ester reaction mixture is heated to a temperature of 165xc2x0 C. to 220xc2x0 C. for up to 120 minutes while optionally removing volatiles. Subsequent to the heating step a multivalent alcohol is added to the reaction mixture. The multivalent alcohol can be added in a single addition step or over time. Preferably the alcohol is added at a rate such that the temperature of the reaction mixture is maintained in the 165xc2x0 C. to 220xc2x0 C. range. Most preferably the alcohol is pumped into the reaction mixture at a rate so that the temperature of the reaction mixture is maintained in the desired range. The condensation reaction of the alcohol and half ester is carried out with removal of volatiles. The condensation reaction is carried out to a predetermined acid value generally between 5 and 45. When prepared according to the invention the formation of gel particles is reduced or the gel particles are completely eliminated. No prereaction of the DCPD is needed. No additional oxidation or polymerization preventing agents or inhibitors other than those present in the commercially available raw materials need be added during the preparation of the half ester.
Not Applicable
The present invention relates to a process of preparing polyester resins preferably using low grade DCPD. The resins prepared according to the process of the invention have reduced levels of gel particles. In a process of the invention where the reactor is sealed during heating prior to addition of the glycols the resin product contains about 10% by weight or less of the amount of gel particles based on the total weight of the undiluted resin, typically produced in resins prepared using low grade DCPD by known methods of preparation. In a preferred version of the process where volatiles are removed during the heating step that is performed after the half ester reaction step and prior to addition of glycols gel particle content is reduced to less than 0.01% by weight in filtration residue based on the total weight of the undiluted resin. In many instances gel particles are not detectable in the filter residue.
In the first step of the process DCPD preferably low grade DCPD and a carboxylic acid having at least two carboxy functional groups or the corresponding anhydride are reacted in the presence of water. From 1% to 100% by weight of the carboxylic acid or corresponding anhydride contain ethylenic unsaturation. The reaction can be carried out at any temperature at which the formation of the half ester proceeds. Generally a temperature between 50xc2x0 C. and 150xc2x0 C. is used. A preferred temperature range is from 70xc2x0 C. to 140xc2x0 C. In a more preferred embodiment the temperature of the half ester reaction mixture is carried out at a maximum temperature of 132xc2x0 C. The reaction to form the half ester is continued until a majority of the DCPD is reacted. Acid value is a convenient method of monitoring the reaction. The predetermined acid value signifying the point at which a majority of the DCPD has reacted will depend on the composition of the specific reaction mixture. For example, if 1 mole of DCPD is reacted with one mole of maleic anhydride in the presence of 1.1 moles of water the acid value target (using ASTM test method D 1639-90) would be 210 to 240. A preferred acid value range for the present process is from 210 to 260. When the predetermined acid value range has been reached for the half ester reaction mixture the mixture is heated to a temperature of from 165xc2x0 C. to 220xc2x0 C., preferably from 180xc2x0 C. to 205xc2x0 C., most preferably 195xc2x0 C. Typically the reaction mixture is heated to temperature at a rate of 0.1 to 4.0xc2x0 C. per second. After heating to the desired temperature the reaction mixture is held at temperature for up to 120 minutes. Preferably the mixture is held at temperature for up to 90 minutes. And most preferably the reaction mixture is held at temperature for up to 45 minutes. It was determined that a hold time is not needed at temperatures of 195xc2x0 C. and above. However, the half ester reaction mixture is generally held at the desired temperature for 15 minutes to ensure that gel particles are not formed. Both the half ester formation step and heating step are carried out at atmospheric pressure without removal of volatiles. However either or both steps can be carried out at sub- or super atmospheric pressure with the optional removal of volatiles and under an inert atmosphere. Examples of which include simple distillation, distillation with nitrogen sparge or vacuum stripping.
On completion of the heating step a multivalent alcohol is added to the half ester reaction mixture. The alcohol can be added in a single addition or incrementally. Although the reaction mixture can be allowed to cool, it is preferred to add the alcohol incrementally so as to maintain the 165xc2x0 C. to 220xc2x0 C. temperature of the reaction mixture. After completion of the addition of the alcohol the reaction mixture is allowed to react at temperature with removal of volatiles until a predetermined acid value is obtained for the resin mixture. Volatiles can be removed by any convenient means. The predetermined acid value of the alcohol reaction mixture will depend on the desired handling characteristics of the resin. Typical ranges for acid values can be between 5 and 45, preferably between 10 and 40, most preferably between 10 and 35.
On completion of the reaction to form the DCPD modified polyester resin the resin is cooled and diluted with a soluble monomer such as styrene. Commonly used additives such as polymerization inhibitors and the like can be added at this point. If filtration to remove gel particles is necessary it is usually performed prior to pumping the diluted resin to storage. Filtration in commercial operations is usually done by pumping the diluted resin through a 100 to 200 micron bag filter.
The object of the invention is to provide a process to prepare DCPD modified unsaturated polyester resins with little or no gel particle content preferably from the more economical low grade DCPD. Low grade DCPD has greater than 0.1% by weight C-5 trimer. A typical range of trimer content for low grade DCPD is from greater than 0.1% by weight to 2.0% by weight. Examples of low grade DCPD includes those available from Equistar designated as DCPD 100 and 101.
Examples of ethylenically unsaturated carboxylic acids containing at least two carboxy functional groups or their corresponding anhydrides include maleic acid, fumaric acid, itaconic acid, maleic anhydride and mixtures thereof. In addition other acids, anhydrides or esters of the acids can be used in the process. Examples of such acids include phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, phthalic anhydride and the like. Maleic acid or maleic anhydride are preferred. Water is present in order to ensure that any anhydride present is hydrolyzed to the corresponding acid.
A wide variety of multivalent alcohols can be used in the process of the invention. Examples would include common diols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-propanediol, 1,4-butanediol, and polyoxyalkylene alkylene glycols. Triols and higher functional polyols such as glycerol, trimethylol propane and oxyalkylated adducts thereof can also be used.
Other components used with the resins are those known in the art and include soluble monomers, catalysts and inhibitors. The monomers include but are not limited to (meth)acrylate esters such as methylmethacrylate and substituted styrenes such as vinyl toluene and styrene. Styrene is a preferred monomer. Catalysts for esterification and to aid in the maleate to fumarate isomerization can be added. Examples of isomerization catalysts include morpholine, piperidine, and the like. Examples of esterification catalysts include mineral acids, methanesulfonic acid, toluenesulfonic acid as well as Lewis acids and zinc acetate. Commonly used inhibitors include hydroquinone, p-benzoquinone, di-t-butylhydroquinone, t-butylcatechol, phenothiazine, and the like.
The DCPD modified unsaturated polyester resins prepared according to the process of the present invention can be used in any applications in which DCPD modified unsaturated polyester resins are normally used. Examples of such uses include SMC, RTM, preparation of fiberglass reinforced boats, whirlpool baths, etc.
Having thus described the invention the following examples are provided as illustrations of the invention and should not be construed as limiting in nature.
ASTM D1639-90 was used to determine acid values. ASTM 1545-89 was used to determine the viscosity of the styrene diluted resin unless specifically noted otherwise Following are examples of a generic standard procedures and embodiments of the process of the invention.
Procedure I (Standard Procedure)
71.9 g of water and 506.85 g DCPD 101 having greater than 0.1%by weight trimer is charged to a reactor with stirring and heated to 65xc2x0 C. After heating 202.3 g of maleic anhydride is added to the reaction vessel. The reaction is exothermic. The temperature is not allowed to exceed 132xc2x0 C. After the exotherm is complete and the temperature is below 100xc2x0 C. an additional 165.5 g of maleic anhydride is added to the reaction vessel. A temperature of 125xc2x0 C. is maintained for 30 minutes. When an acid value of 230 to 260 is obtained for the half ester reaction mixture glycol and 50 ppm hydroquinone are added to the reaction mixture and the contents of the vessel are heated to 195xc2x0 C. with removal of volatiles. The reaction is allowed to run until the resin has an acid value of between 18 and 35 and a stokes viscosity of 11 to 14 (75/25, resin/styrene w/w). The resin is allowed to cool to 100xc2x0 C. and 333.5 g of styrene containing 0.09 g of toluhydroquinone (THQ), and 0.05 g of butylated hydroxy toluene (BHT) dissolved in glycol ether are added.
Procedure II
71.9 g of water and 506.85 g DCPD having greater than 0.1% by weight trimer is charged to a reactor with stirring and heated to 65xc2x0 C. After heating, 202.3 g of maleic anhydride is added to the reaction vessel. The reaction is exothermic. The temperature is not allowed to exceed 132xc2x0 C. After the exotherm is complete and the temperature is below 100xc2x0 C. an additional 165.5 g of maleic anhydride is added to the reaction vessel. A temperature of 125xc2x0 C. is maintained for 30 minutes. When an acid value of 230 to 260 is reached the reactor is sealed and heated to a temperature of from 165xc2x0 C. to 220xc2x0 C. and held at temperature for up to 90 minutes. After heating and holding at temperature glycol(s) and 50 ppm hydroquinone are added to the reaction vessel at a temperature of between 180xc2x0 C. to 220xc2x0 C. with removal of volatiles. The reaction is allowed to continue until the resin has an acid value of from 18 to 35 and a stokes viscosity of from 11 to 14 (75/25 resin/styrene). The resin is allowed to cool to 100xc2x0 C. and 333.5 g of styrene, containing 0.09 g of toluhydroquinone (THQ), and 0.05 g of butylated hydroxy toluene (BHT) dissolved in glycol ether are added.
Procedure III
71.9 g of water and 506.85 g DCPD having greater than 0.1% by weight trimer is charged to a reactor with stirring and heated to 65xc2x0 C. After heating, 202.3 g of maleic anhydride is added to the reaction vessel. The reaction is exothermic. The temperature is not allowed to exceed 132xc2x0 C. After the exotherm is complete and the temperature is below 100xc2x0 C. an additional 165.5 g of maleic anhydride is added to the reaction vessel. A temperature of 125xc2x0 C. is maintained for 30 minutes. When an acid value of 230 to 260 is reached the reaction mixture is heated to a temperature of from 165xc2x0 C. to 220xc2x0 C. with removal of volatiles and held at temperature for up to 120 minutes. After heating and holding at temperature glycol(s) and 50 ppm hydroquinone are added to the reaction vessel at a temperature of between 165xc2x0 C. to 220xc2x0 C. with removal of volatiles. The reaction is allowed to continue until the resin has an acid value of from 18 to 35 and a stokes viscosity of from 11 to 14 (75/25 resin/styrene). The resin is allowed to cool to 100xc2x0 C. and 333.5 g of styrene, containing 0.09 g of toluhydroquinone (THQ), and 0.05 g of butylated hydroxy toluene (BHT) dissolved in glycol ether are added.
Procedure IV
71.9 g of water and 506.85 g DCPD having greater than 0.1% by weight trimer is charged to a reactor with stirring and heated to 65xc2x0 C. After heating, 202.3 g of maleic anhydride is added to the reaction vessel. The reaction is exothermic. The temperature is not allowed to exceed 132xc2x0 C. After the exotherm is complete and the temperature is below 100xc2x0 C. an additional 165.5 g of maleic anhydride is added to the reaction vessel. A temperature of 125xc2x0 C. is maintained for 30 minutes. When an acid value of 230 to 260 is reached the reaction mixture is heated to a temperature of from 165xc2x0 C. to 220xc2x0 C. with removal of volatiles and held at temperature for up to 120 minutes. After heating and holding at temperature 50 ppm hydroquinone is added and glycol(s) are pumped into the reaction vessel over a period of time ranging from 30 minutes to 3 hours at a temperature of between 180xc2x0 C. to 220xc2x0 C. with removal of volatiles. The reaction is allowed to continue until the resin has an acid value of from 18 to 35 and a stokes viscosity of from 11 to 14 (75/25 resin/styrene). The resin is allowed to cool to 100xc2x0 C. and 333.5 g of styrene, containing 0.09 g of toluhydroquinone (THQ), and 0.05 g of butylated hydroxy toluene (BHT) dissolved in glycol ether are added.
Procedures II-IV, procedures according to the invention yield resins with reduced levels of gel particles when compared to the resin prepared by the standard process of Procedure I.